1. Field
The subject matter disclosed herein relates to an apparatus, system and method of enabling corneal topography by mobile communication and/or computing devices, and more specifically a smartphone.
2. Information/Background of the Invention
Corneal topography has evolved to become a key diagnostic modality in numerous sectors of eye care including routine eye examination, evaluation for laser refractive surgery (LASIK and PRK), evaluation for cataract and lens implant surgery, and evaluation or monitoring of numerous corneal disease states including keratoconus. Commercial corneal topography devices currently in use typically incorporate an illuminated series of concentric rings (a “placido disc”) viewed coaxially by a cornea being tested. A digitized image is obtained of the reflected rings.
Most commercially available corneal topography systems evolved as standalone diagnostic instruments connected to a dedicated personal computer. The placido disc is mounted in front of an apparatus for stabilization of the subject's head, typically situated on a special motorized table intended to be positioned comfortably in front of a seated patient. The rings image is processed by proprietary software resident on the computer to which a placido disc system is affixed, and is typically stored locally on the dedicated computer or a network server in association with patient identifying information for later retrieval, comparison, and additional analysis. Power maps and other derivative analyses are typically displayed on a computer monitor, and are output to a printer or communicated electronic medical record (“EMR”) databases in various formats. The relative high cost ($8,000 to over $50,000) and specialized nature of these devices causes their use to be largely limited to the offices of corneal specialists, laser vision correction surgeons, cataract surgeons, and offices of eye care professionals (ophthalmologists or optometrists) performing a large number of routine eye examinations.
Relative high cost and lack of portability inherently limit the reach of corneal topography to other healthcare professionals who may desire to use this diagnostic modality for screening purposes or other applications. For instance, keratoconus is a condition characterized by abnormalities of corneal topography including asymmetry of topographic power, abnormal maximum central steepness, reduced corneal thickness in the apex of the “cone” or zone of maximum steepness, and decentered corneal apex, among other abnormalities. The incidence of keratoconus in the general population is estimated to be in the range of 1 in several hundred. Keratoconus typically becomes manifest in the age range 18-26 years, and occasionally in younger patients. Therefore, there is reason for pediatricians and school nurses, among other groups, to have access to a cost-effective, portable method to screen for this condition.
U.S. Pat. No. 5,526,073 discloses a small cone corneal topographer with concentric black and white rings. The corneal vertex location in this method was based on the vertex breaking a beam of light. This method described in this patent suffers from a trade-off of allowing a wide object field of view and small rings in the center of the cornea.
U.S. Pat. No. 7,465,049 discloses several ophthalmic systems utilizing a cellular phone. The method and corneal topography system described in U.S. Pat. No. 7,465,049 does not include a ring target generation technique where both a wide object field of view and small reflected rings are provided.
U.S. Pat. No. 9,036,282 discloses a method for attaching a lens to a system such as a smartphone. This method disclosed in U.S. Pat. No. 9,036,282 is very general and does not describe how it could be used with a portable corneal topography system.
U.S. Pat. No. 9,066,683 discloses a method of using a smartphone with a custom hardware module for measuring the wavefront of an eye. The method disclosed in U.S. Pat. No. 9,066,683 does not describe how it could be applied to a portable corneal topography system.
U.S. Pat. No. 9,163,936 discloses a three-dimensional surface profilometer for use in metrology and other applications. The methods disclosed in U.S. Pat. No. 9,163,936 describes the use of a smartphone, but do not describe how they could be applied to realize a reflected ring corneal topography system.
A system is described in a thesis entitled “An Accessible Approach to Corneal Topography”; Andre Luis Beling da Rosa. This system uses a concentric ring target and is integrated with a smartphone, but it does not simultaneously observe a wide object field of view, measure small central corneal zones, and provide for location of the corneal vertex during image acquisition.
“Design and Development of an Ultraportable Corneal Topographer for a Smartphone as a Low Cost New Tool for Preventing Blindness Caused by Keratoconous” by Pinheiro et al. (“Pinheiro”) discloses a corneal topography system that employs a 3D printed ring target and shell to allow attachment to a smartphone. This system does not simultaneously observe a wide object field of view, measure small central corneal zones, and provide for location of the corneal vertex during image acquisition. The limitations of the systems described above are overcome by our invention, the description which is provided below.